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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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of the essential components, namely, silica, alumina and ferric oxide (the sum of
which is not less than 80%), in order that it may be calculated in what ratio it
must be mixed with the other raw materials, and (2) on the amounts of lime and
other impurities which may be harmful to the cement.


Tuw. pozzolanc arc readily friable, volcanic materials which, when mixed
with lime, form mortars capable, of setting even under water. Their essential
components arc1, silica, alumina and ferric oxide, and they contain also lime,
magnesia and alkalies, together with a, considerable amount of combined
water. The more important and the best known arc* (i) those, from the
neighbourhood of Rome, which are distinguished as red (brownish red or
violet red), black (dark brown or grey) and po/,/olanclle (greyish or reddish,
of more recent formation), and (2) those from near Naples, which are
usually light grey but sometimes dark grey. Po/./oUme are also found in
the Auvergne and other volcanic regions. With the po/,/,olune are grouped
other similar materials, such as sitn/orin, found in the island of that name
and in other Greek islands, and /WN.S, which occurs in the Hifel and in other
districts on the banks of the Rhine ; both of these, are greyish. There are
also non-vole a i tic jwzrsola-iic, composed of the detritus of various siliceous
rocks, but their use is somewhat limited.

The name Miificial pozwhinc- is given to substitutes for po/,/,olana;
these are obtained by calcination of clay, schist, basalt, etc., but use is
made principally of blast-furnace slag, which is granulated by pouring it
into water direct from the furnace.

The testing of po/,/ and slags includes quantitative chemical analysis
and, especially for pox/olane, certain tests indicated below.


1.   Chemical Analysis

Chemical analysis of po/x.olane and slags may be made by the methods
already described for the analysis of clays, determinations being made of
the moisture, the loss on ignition, the silica, alumina, and ferric oxide (also
any manganese! oxide), lime, magnesia, alkalies (also any sulphates and,
especially in slags, sulphides). As regards the loss on ignition, in good
po/,y,olune this is composed almost entirely of the combined water, since
carbon dioxide is not usually present in appreciable quantity. The1 com-
bined water is an important factor with the poiwolane, standing in close
relation to their hydraulic properties.

Further, in sonic; cases, it is necessary to determine, the constituents ol
the silicates of poxHolune attackable by hydrochloric, acid and of those, non-
attackable. In this event, a •*] grains of the substance are treated with
hydrochloric acid in the same way us the limestones and marls (</,?'., Com-
plete Analysis, (>, a). The undeeomposed residue will contain the sand, the
undccomposed silicates and the silica of the silicates which have been
attacked; the bases corresponding with the last are found in the filtrateulphides.—These are determined as with limestone